1. Field of the Invention
This invention relates generally to the injection of fluid into oil and gas wells. In particular, this invention relates to the delivery of fluid to a well through a production tree mounted on the well, by injecting the fluid through a mandrel in the production tree.
2. Brief Description of Related Art
The production of oil and gas from some wells may lead to contact between compounds in hydrocarbon rock formations, and those present in oilfield process fluids, such as, for example, seawater. This contact may lead to the formation of “scale”, or salts that clog the formation and inhibit hydrocarbons in the formation from entering the well. Accordingly, scale inhibitors are sometimes introduced into a well to control or prevent scale deposition. In some cases, scale inhibitors may be combined with fracture treatments, whose purpose is to crack the formation and facilitate the release of hydrocarbons into the well.
The fluids used to inhibit scaling and to cause fracturing (hereinafter referred to as scale squeeze fluid, or just fluid) are typically introduced to the well through the choke of a production tree attached to the well. From the choke, the fluid may enter the production bore of the tree, the production tubing of the well, and ultimately the formation in need of de-scaling/fracturing. However, there are problems associated with introducing the fluid through a choke on the production tree.
For example, when the fluid is introduced through the choke, the capacity of the choke to carry out other functions, such as managing pressure within the well, may be reduced or eliminated. In addition, introduction of the fluid through the choke requires a special choke insert adapted for interface with a landing module that delivers the fluid. Retrofitting the choke to accept the special choke insert can be a complicated process that requires multiple steps. The steps include running guide posts, running a remote component replacement (RCR) tool to remove any old choke inserts, running an RCR tool to insert the special choke insert, running a scale squeeze module, injecting the scale squeeze fluid, recovering the module, and capping the scale squeeze adapter.
Accordingly, there is a need for a fluid injection system and process that overcomes the disadvantages of the prior art.